1. Field of the Invention
The present invention relates to a tunnel magnetoresistive element, and a low-power-consumption, nonvolatile magnetic memory provided with the same.
2. Description of the Related Art
As the tunnel magnetoresistive element to be employed in a highly integrated magnetic memory in the future, known are a tunnel magnetoresistive element using an oxide of Al for an insulating barrier layer (T. Miyazaki and N. Tezuka, J. Magn. Magn. Mater. 139, L231 (1995)), and a tunnel magnetoresistive element using magnesium oxide for an insulating barrier layer (S. Yuasa. et al., Nature Material 3, 868 (2004)). The latter tunnel magnetoresistive element provides a magnetoresistance ratio several times larger than that of the former one. Furthermore, a tunnel magnetoresistive element using CoFeB for a magnetic layer, and a low-power-consumption magnetic memory cell and magnetic random access memory using the tunnel magnetoresistive element are disclosed in Japanese Patent Application Publication No. 2006-269530. Moreover, the conventional nonvolatile magnetic memory is configured of a memory cell in which a tunnel magnetoresistive element is formed on a MOSFET. This is a method, in which the MOSFET is used for switching, and with the use of a current-induced spatial magnetic field which is generated by passing a current through a bit line and a word line, the magnetization direction of the tunnel magnetoresistive element is rotated in order to write information, and the information is read out using an output voltage of the tunnel magnetoresistive element.
Moreover, besides the magnetization rotation using the current-induced spatial magnetic field, known is a so-called spin-transfer torque magnetization reversal method, or synonymously, a spin injection magnetization reversal method, in which the magnetization is rotated by passing a current directly through the magnetoresistive element. This is disclosed in the specification of the U.S. Pat. No. 5,695,864 and Japanese Patent Application Publication No. 2002-305337, for example. Japanese Patent Application Publication No. 2005-294376 discloses a tunnel magnetoresistive element using a free layer having a plurality of ferromagnetic layers stacked with a nonmagnetic layer interposed therebetween in order to stably cause the spin-transfer torque to reverse the magnetization against a penetrating magnetic field from the outside.